In a braking device for pressing a rotating member that rotates together with an output shaft against a fixed member fixed to a vehicle body to generate a braking force, the rotating member generates heat due to friction. Therefore, a lubricant is applied between the rotating member and the fixed member, thereby cooling the rotating member and suppressing increase in temperature of the rotating member.
In an instance where there is a large amount of lubricant between the rotating member and the fixed member, there is a possibility that a part of the driving force of the output shaft may be transferred from the rotating member to the lubricant, resulting in a loss of driving force, even when the braking device is in a non-braking state in which the rotating member and the non-rotating member are not pressed against each other.
In order to prevent such a loss of driving force, a lubricant circuit that increases the amount of supplied lubricant when the braking device is in a braking state, and decreases the feed amount when the braking device is in a non-braking state, is provided according to a technique described in Japanese Laid-open Patent Application No. 53-034054.